A fruit sizer is used to automatically separate fruit according to its size. Typically, the sizer is used in conjunction with a grade table so that the outlet of the grade table connects to the inlet of the sizer. The grade table is used to allow human graders to cull out damaged fruit. A sizer, on the other hand, does not require human input and the sizing is done automatically.
The conventional sizer comprises a plurality of parallel conveyor paths which carry fruit from one end of the sizer to the other. As the fruit is carried along the conveyor belt, it comes into contact with a sizing roller which is spaced from the conveyor belt by an amount equal to the maximum size of the fruit desired to be separated from the remainder of the fruit. The roller rotates in a direction to push fruit out of the gap between the sizing roller and the conveyor, thus acting to jostle the fruit to ensure that all pieces of fruit eventually confront the gap between the sizing roller and the belt. When a piece of fruit is smaller than this gap, it falls through the gap and is carried away from the sizer by any of several known means, such as a second conveyor located below the sizer.
The prior art sizers employ a conveyor path which is tilted with respect to the horizontal so that the fruit is continually urged against the sizing roller and so that the fruit falls between the gap under the force of gravity. This has created a problem in the prior art sizers since the roller which drives the conveyor belt rotates about a horizontal axis, resulting in a twist in the conveyor belt. This twist creates an uneven strain on the belt, resulting in the belt's movement off of the rollers, and this movement is prevented by allowing one edge of the belt to rub against a stop. This constant rubbing between the belt and the stop causes great wear on the belt, resulting in a reduced lifetime.
The conventional drive mechanism for rotating the sizing rollers includes a driving pulley which operates through a plurality of separate chains to drive the sizing rollers. This mechanism is clumsy and requires numerous sprockets and chains which require lubrication.